Let say that we enter Mists... get to 90, start doing heroics we get some JPs and buy some nice gear to get into the current raid tier. Right?
OK - so... what happens when the next tier of Raiding opens up? Normally the previous valor gear becomes purchasable via JP (to get new players quickly into the next tier).
But this time... there are no Valor items. New players/alts now loose that path to get them up to speed with the current raiding guild (or quickly, at least...).
So, then, erm... what do we buy with our JPs then come next raid tier? Is it just the older heroic dungeon gear and that's it? Does that "for great justice" guild perk become useless after the first raiding tier? Or is there here going to be other uses for Justice Points for that AREN'T raid/gear specific purchases? I'm not sure enough people will want to run dungeons just to buy trade mats via extremely overpriced JP values.